Thermally expandable microcapsule, hollow particle, and foam

Abstract

The purpose of the present invention is to provide a thermally expandable microcapsule, a hollow particle, and a foam that allow tracking of the source of carbon dioxide while having sufficient foaming performance. The present invention is a thermally expandable microcapsule in which a volatile expanding agent is encapsulated as a core agent in a shell, wherein the ratio of carbon-14 (14C) to the total carbon (C) constituting the thermally expandable microcapsule (14C / C) is 4.0×10-14 or more.

Description

Thermally expandable microcapsules, hollow particles and foams

[0001] The present invention relates to thermally expandable microcapsules, hollow particles, and foams.

[0002] To date, resin materials have been foamed using blowing agents to reduce their weight and improve their functionality, and thermally expandable microcapsules and chemical blowing agents have generally been used as such blowing agents. Thermally expandable microcapsules are used in a wide range of applications, including as design-imparting agents and lightweighting agents, and are also used in foaming inks, wallpapers, and other lightweight paints.

[0003] As such thermally expandable microcapsules, those in which a liquid volatile blowing agent that becomes gaseous at a temperature below the softening point of the shell polymer is encapsulated in a thermoplastic shell polymer are widely known. For example, Patent Document 1 discloses a method for producing thermally expandable microcapsules encapsulating a volatile blowing agent by adding, with stirring, an oil-based mixture in which a volatile blowing agent such as a low-boiling-point aliphatic hydrocarbon is mixed with a monomer, together with an oil-soluble polymerization catalyst, to an aqueous dispersion medium containing a dispersant, and then performing suspension polymerization.

[0004] Special Publication No. 42-26524

[0005] In recent years, carbon dioxide emissions have been restricted as a measure against global warming. Carbon footprint (CFP) in particular has become a focus of attention. However, because foams are based on resin, carbon dioxide is emitted during production and disposal. To calculate CFP, it is necessary to identify the products and processes from which carbon dioxide is emitted. However, this information is not currently fully understood, creating the challenge of not knowing which processes should be targeted for reducing carbon dioxide emissions.

[0006] An object of the present invention is to provide thermally expandable microcapsules, hollow particles, and foams that have sufficient foaming performance and that allow the source of carbon dioxide to be traced.

[0007] Disclosure 1 provides a thermally expandable microcapsule having a shell containing a volatile expanding agent as a core agent, wherein the carbon content of the thermally expandable microcapsule is 14 ( １４ C) abundance ratio ( １４ C / C) is 4.0 x 10 －１４ Disclosure 2 is the thermally expandable microcapsule according to Disclosure 1, wherein the shell is made of a polymer of a monomer composition containing at least one monomer selected from the group consisting of nitrile-based monomers and monomers having a carboxyl group. Disclosure 3 is the thermally expandable microcapsule according to Disclosure 2, wherein the shell is made of a polymer of a monomer composition containing at least one monomer selected from the group consisting of nitrile-based monomers and monomers having a carboxyl group. １４ Nitrile monomers containing C and １４ The thermally expandable microcapsule according to Disclosure 1 is made of a polymer of a monomer composition containing at least one monomer selected from the group consisting of crosslinkable monomers containing C. Disclosure 4 is a thermally expandable microcapsule according to any one of Disclosures 1 to 3, having a volume average particle size of 20 μm or more. Disclosure 5 is a thermally expandable microcapsule according to any one of Disclosures 1 to 4, having a foaming initiation temperature (Ts) of 132°C or more and 170°C or less. Disclosure 6 is a thermally expandable microcapsule according to any one of Disclosures 1 to 5, having a maximum foaming temperature (Tmax) of 170°C or more and 220°C or less. Disclosure 7 is a thermally expandable microcapsule according to any one of Disclosures 1 to 5, wherein the volatile blowing agent is １４ The thermally expandable microcapsule according to any one of Disclosures 1 to 6, further comprising carbon 14 (C) relative to the total carbon (C) constituting the hollow particle. １４ C) abundance ratio ( １４ C / C) is 4.0 x 10 －１４ Disclosure 9 is a foam having cells dispersed in a resin, the cells of the foam being formed by thermal expansion of thermally expandable microcapsules each having a polymer-containing shell and a volatile liquid encapsulated as a core agent, and the ratio of carbon 14 ( １４ C) abundance ratio ( １４ C / C) is 1.0 x 10 －１４ The foam is as described above. The present invention will be described in detail below.

[0008] As a result of extensive research, the present inventors have found that the ratio of carbon 14 ( １４ C) abundance ratio ( １４ The present inventors have found that by setting the ratio C / C within a predetermined range, it is possible to obtain thermally expandable microcapsules that have sufficient foaming performance and that enable tracing of the source of carbon dioxide, and have thus completed the present invention.

[0009] The carbon that makes up carbon dioxide circulating in the Earth's environment is an isotope, radioactive carbon-14 (hereinafter referred to as １４ C), stable carbon-12 (hereinafter, １２ C), metastable carbon-13 (hereinafter, １３ C) a mixture of the following in terms of mass ratio: １２ C is 98.892% by mass, １３ C is 1.108% by mass, １４ C is 1.2 x 10 －１２ Mass%~1.2×10 －１０ It is known to be a trace amount by mass. １２ C and １３ The ratio of C is stable. １４ C is the neutrons contained in secondary cosmic rays generated by primary cosmic rays in the upper atmosphere that react with nitrogen atoms in the atmosphere ( １４ N), so although it fluctuates slightly depending on the strength of sunspot activity, it is constantly being supplied, but on the other hand, it decreases with a half-life of 5,730 years. １４ The mass ratio of C in the carbon dioxide circulating in the Earth's environment is isolated from the present-day carbon dioxide circulating in the Earth's environment. １４ This is a very small value compared to the mass ratio of C. Therefore, the ratio of carbon 14 ( １４ C) abundance ratio ( １４ When the thermally expandable microcapsules of the present invention having a C / C ratio within a predetermined range are used, １４ By detecting C, it is possible to track which product or process emitted carbon dioxide.

[0010] The thermally expandable microcapsules of the present invention are characterized in that the ratio of carbon 14 ( １４ C) abundance ratio ( １４ C / C) is 4.0 x 10 －１４ That's all. １４ C / C is 4.0 x 10 －１４ By satisfying the above, it becomes possible to track the source of carbon dioxide while maintaining sufficient foaming performance. １４ The preferred lower limit of C / C is 4.0 × 10 －１３ , and a more preferable lower limit is 4.0 × 10 －１２ , and a more preferable lower limit is 5.0 × 10 －１２ The above １４ The larger the C / C, the better, but it circulates within the global environment. １４ C is 1.2 x 10 －１２ Mass%~1.2×10 －１０ Since it is a trace amount by mass, it is generally 1.2 × 10 －１１ From the viewpoint of cost, the preferred upper limit is 1.0 × 10 －１１ , and a more preferable upper limit is 9.0×10 －１２ Note that total carbon is the sum of all carbon isotopes, １４ C / C is the ratio of carbon to total carbon １４ The abundance ratio of C. １４ C / C means the mass ratio.

[0011] As mentioned above in this specification １４ For example, the C / C is prepared by converting the thermally expandable microcapsules into carbon dioxide or graphite as necessary, and then measuring the C / C relative to a standard substance (e.g., oxalic acid from the NIST in the United States) by accelerator mass spectrometry (AMS). １４ It can be determined by comparatively measuring the C content. １４ C / C is the １４ It can be calculated by dividing the amount of C by the total amount of carbon in the sample.

[0012] In the present invention, the shell of the thermally expandable microcapsule １４ C / C and core １４ Difference between C / C [(in the core１４ C / C)-(shell １４ C / C)] is preferably 0.01 or more, more preferably 0.3 or more, even more preferably 0.45 or more, and even more preferably 0.5 or more. There is no particular upper limit, but it is preferably 0.9 or less. By setting it in the above range, the " １４ The difference in C / C allows us to distinguish whether carbon dioxide emissions in the foam manufacturing process are coming from the core or from shell decomposition.

[0013] In the present invention, the shell of the thermally expandable microcapsule １４ C / C in core １４ C / C ratio [(in the core １４ C / C) / (shell １４ C / C)] is preferably 0 or more, more preferably 1.0 or more, even more preferably 1.5 or more, even more preferably 1.85 or more, and particularly preferably 2.0 or more. There is no particular upper limit, but it is preferably 15 or less. By setting it in the above range, the " １４ The difference in C / C allows us to distinguish whether carbon dioxide emissions in the foam manufacturing process are coming from the core or from shell decomposition.

[0014] In the present invention, by adjusting the components of the monomer and volatile expanding agent that constitute the shell of the thermally expandable microcapsule, １４ It is possible to control the C / C ratio. １４ Using a monomer containing C, １４ Using an additive containing C, １４ It is preferable to use a volatile expanding agent containing C. In addition, the thermally expandable microcapsules prepared by the existing method １４ Surface treatment using a material containing C, １４ By covering the thermally expandable microcapsules with a coating containing a material containing C, １４ The C / C can be controlled.

[0015] The thermally expandable microcapsules of the present invention have a maximum foaming temperature (Tmax) of preferably 170°C (lower limit) and 220°C (upper limit). By setting the temperature within the above range, heat resistance is improved, and when a composition containing the thermally expandable microcapsules is molded at high temperatures, the thermally expandable microcapsules can be prevented from bursting or shrinking. Furthermore, aggregation of the thermally expandable microcapsules during molding can be suppressed, resulting in a good appearance. A more preferred lower limit is 175°C, an even more preferred lower limit is 180°C, and a more preferred upper limit is 215°C, and an even more preferred upper limit is 210°C. In this specification, the maximum foaming temperature refers to the temperature at which the diameter of the thermally expandable microcapsule reaches its maximum (maximum displacement) when the diameter is measured while heating the thermally expandable microcapsule from room temperature. The temperature at which the displacement begins to increase is referred to as the foaming initiation temperature.

[0016] The foaming initiation temperature (Ts) preferably has a lower limit of 132°C and an upper limit of 170°C. By setting the temperature within the above range, foaming becomes easy and a desired foaming ratio can be achieved. A more preferred lower limit is 135°C, an even more preferred lower limit is 140°C, and a more preferred upper limit is 165°C, and an even more preferred upper limit is 160°C.

[0017] Furthermore, the thermally expandable microcapsules of the present invention have a maximum displacement (Dmax) measured by thermomechanical analysis of preferably 10 μm, more preferably 20 μm, even more preferably 100 μm, even more preferably 200 μm, particularly preferably 300 μm, and particularly preferably 500 μm. The higher the upper limit, the better; however, generally, the upper limit is preferably 4000 μm, more preferably 3000 μm, even more preferably 2000 μm, even more preferably 1800 μm, and particularly preferably 1500 μm. By keeping the Dmax within the above range, the expansion ratio is improved and the desired expansion performance is obtained. The maximum displacement refers to the value at which the diameter of a predetermined amount of thermally expandable microcapsules is maximized when the diameter is measured while heating a predetermined amount of thermally expandable microcapsules from room temperature. The Tmax, Ts, and Dmax can be measured using a thermomechanical analyzer (TMA).

[0018] The preferred lower limit of the volume average particle diameter of the thermally expandable microcapsules of the present invention is 3 μm, more preferably 5 μm, even more preferably 10 μm, even more preferably 15 μm, particularly preferably 18 μm, especially preferably 20 μm, and the preferred upper limit is 50 μm, more preferably 45 μm, even more preferably 40 μm, even more preferably 35 μm, especially preferably 30 μm. By keeping the volume average particle diameter within the above ranges, the resulting molded product can have an appropriate amount of bubbles, a sufficient expansion ratio, and excellent appearance. Furthermore, the CV value of the volume average particle diameter of the thermally expandable microcapsules of the present invention is preferably 35% or less, usually 10% or more, and preferably 15% or more. The volume average particle diameter and CV value can be measured using a particle size distribution diameter measuring instrument or the like.

[0019] The shell constituting the thermally expandable microcapsules of the present invention is preferably composed of a polymer obtained by polymerizing a monomer composition containing a monomer. The monomer composition preferably contains a nitrile-based monomer or a monomer having a carboxyl group. That is, the shell is preferably composed of a polymer of a monomer composition containing at least one monomer selected from the group consisting of nitrile-based monomers and monomers having a carboxyl group. The monomer composition more preferably contains a nitrile-based monomer and a monomer having a carboxyl group. The monomer composition even more preferably contains a nitrile-based monomer, a monomer having a carboxyl group, and a (meth)acrylic acid ester monomer. The monomer composition even more preferably contains a nitrile-based monomer, a monomer having a carboxyl group, a crosslinkable monomer, and a (meth)acrylic acid ester monomer. The monomer composition may also contain other monomers in addition to the nitrile-based monomer, the monomer having a carboxyl group, the crosslinkable monomer, and the (meth)acrylic acid ester monomer.

[0020] In the present invention, the shell is １４It is preferable that the shell is made of a polymer obtained by polymerizing a monomer composition containing a monomer containing C. In particular, the shell is made of １４ Nitrile monomers containing C and １４ It is preferable that the polymer is made of a monomer composition containing at least one monomer selected from the group consisting of crosslinkable monomers containing C.

[0021] The nitrile monomer is at least one selected from acrylonitrile and methacrylonitrile. By adding the nitrile monomer, the gas barrier properties of the shell can be improved.

[0022] The nitrile monomer is １４ It is preferable that the monomer is a nitrile monomer containing C. １４ Nitrile monomers containing C include: １４ Examples of the acrylonitrile and methacrylonitrile containing C include the above. １４While the method of obtaining or synthesizing C-containing acrylonitrile, methacrylonitrile, etc. is not particularly limited, for example, acrylonitrile, methacrylonitrile, etc. synthesized using biomass materials such as biomass propylene can be used. Biomass materials such as biomass propylene can be broadly divided into two categories based on the plant from which they are derived: those derived from C3 plants such as sweet potato, sugar beet, rice, trees, and algae, and those derived from C4 plants such as corn, sugarcane, and cassava. More than 90% of plants on Earth belong to the C3 category, including agriculturally useful plants such as rice, wheat, tobacco, wheat, potatoes, and palm trees. The enzyme involved in carbon dioxide fixation in the photosynthetic pathway of C3 plants is ribulose-1,5-bisphosphate carboxylase, which has a low affinity for carbon dioxide and a high affinity for oxygen, resulting in low efficiency of the carbon dioxide fixation reaction and, therefore, the photosynthetic reaction. C4 plants are plants that perform C4 photosynthesis, a form of photosynthesis that includes the C4 pathway for carbon dioxide concentration in addition to the Carbene-Benson cycle, a common carbon dioxide reduction pathway, during photosynthesis. The enzyme involved in carbon dioxide fixation in the photosynthetic pathway of C4 plants is phosphoenolpyruvate carboxylase. This enzyme is not inhibited by oxygen, has a high carbon dioxide fixation capacity, and is characterized by the presence of developed chloroplasts in bundle sheath cells. Representative C4 plants include corn, sugarcane, cassava, sorghum, miscanthus, guinea grass, rhodes grass, caramel millet, foxtail millet, barnyard millet, finger millet, and broom tree, which is also known as broom grass, broom tree, and kochia greens. Because these C4 plants use extra energy to fix carbon dioxide, they can fix carbon dioxide more efficiently than non-C4 plants. Furthermore, while non-C4 plants have difficulty collecting carbon dioxide at high temperatures, C4 plants do not experience this problem. Moreover, photosynthesis can be carried out sufficiently even with little water. This is a physiological adaptation that allows plants to cope with harsh climates such as high temperatures, dryness, low carbon dioxide, and nitrogen-poor soil. In addition, from the viewpoint of production volume and cost, corn, sugarcane, and cassava are preferred as the C4 plants. The biomass material is one in which at least a portion of the C in the material is１４ C is fine, １４ A material containing C １４ The material may be made of a material that does not contain C. However, the carbon content of the thermally expandable microcapsules of the present invention is limited to 14 ( １４ C) abundance ratio ( １４ C / C) to 1.0 x 10 －１４ From the viewpoint of facilitating the above, the biomass material is １４ The lower the proportion of C-free materials, the better. １４ It is most preferable that the biomass material is made only of a material containing C. On the other hand, from the viewpoint of reducing costs, the biomass material is １４ It is preferable that the proportion of C-free material is large.

[0023] the above １４ As the nitrile monomer containing C, for example, biomass acrylonitrile manufactured by Asahi Kasei Corporation can be used. １４ The nitrile monomer containing C can be produced, for example, by using biomass propylene as a raw material in a general synthesis method for nitrile monomers. １４ A specific method for producing a nitrile monomer containing C includes, for example, reacting biomass propylene in the presence of ammonia and oxygen in the presence of a solid oxidation catalyst, １４ A method for producing acrylonitrile containing C (Sohio method) can be used. As the biomass propylene, for example, known biomass propylene derived from genetically modified Escherichia coli (manufactured by Mitsui Chemicals, Inc.) can be used.

[0024] The preferred lower limit of the content of the nitrile monomer in the monomer composition is 40% by weight, and the preferred upper limit is 90% by weight. By making it 40% by weight or more, the gas barrier properties of the shell can be improved and the expansion ratio can be increased. By making it 90% by weight or less, heat resistance can be improved and yellowing can be prevented. The more preferred lower limit is 50% by weight, and the more preferred upper limit is 80% by weight.

[0025] The carboxyl group-containing monomer may be a radically polymerizable unsaturated carboxylic acid monomer having a carboxyl group and 3 to 8 carbon atoms, such as one having at least one free carboxyl group per molecule for ionic crosslinking. Specific examples include unsaturated dicarboxylic acids and their anhydrides, and unsaturated dicarboxylic acid monoesters and derivatives thereof. These may be used alone or in combination of two or more. Examples of the unsaturated dicarboxylic acids include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, and cinnamic acid, as well as maleic acid, itaconic acid, fumaric acid, citraconic acid, and chloromaleic acid. Examples of the unsaturated dicarboxylic acid monoesters include monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, monomethyl itaconate, monoethyl itaconate, and monobutyl itaconate. Of these, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, and itaconic acid are particularly preferred. Furthermore, the monomer having a carboxyl group may be １４ A monomer having a carboxyl group containing C may also be used. １４ The method for obtaining a monomer having a carboxyl group containing C is not particularly limited. For example, a monomer synthesized using a biomass material such as biomass olefins such as biomass ethylene and biomass propylene, or bioisobutanol, can be used. １４ A monomer having a carboxyl group containing C can be used.

[0026] The preferred lower limit of the content of the carboxyl group-containing monomer in the monomer composition is 5% by weight, and the preferred upper limit is 50% by weight. By setting the content to 5% by weight or more, the maximum foaming temperature can be increased, and by setting the content to 50% by weight or less, the foaming ratio can be improved. The more preferred lower limit is 10% by weight, and the more preferred upper limit is 30% by weight.

[0027] The monomer composition preferably contains a crosslinkable monomer having two or more double bonds in the molecule. The crosslinkable monomer functions as a crosslinking agent. By containing the crosslinkable monomer, the strength of the shell can be increased, making the cell walls less likely to break during thermal expansion.

[0028] Examples of the crosslinkable monomer include monomers having two or more radically polymerizable double bonds, and specific examples include divinylbenzene, di(meth)acrylate, and tri- or higher functional (meth)acrylates. Examples of the di(meth)acrylate include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate. Other examples include 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, trimethylolpropane di(meth)acrylate, and dimethylol-tricyclodecane di(meth)acrylate. Furthermore, di(meth)acrylate of polyethylene glycol having a weight average molecular weight of 200 to 600 may also be used. Examples of the trifunctional (meth)acrylate include trimethylolpropane tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, triallyl formal tri(meth)acrylate, etc. Examples of the tetrafunctional or higher (meth)acrylate include pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, etc. Among these, trifunctional (meth)acrylates such as trimethylolpropane tri(meth)acrylate and bifunctional (meth)acrylates such as polyethylene glycol provide relatively uniform crosslinking to the acrylonitrile-based shell.

[0029] The crosslinking monomer is １４ It is preferable that the crosslinkable monomer contains C. １４Examples of the crosslinkable monomer containing C include crosslinkable monomers obtained from biomass olefins and biomass (meth)acrylates. １４ There are no particular limitations on the method for obtaining the crosslinkable monomer containing C. For example, it can be synthesized from commercially available biomass (meth)acrylate. Examples of the commercially available biomass (meth)acrylate include n-octyl (meth)acrylate, 2-octyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate, and tetrahydrofurfuryl (meth)acrylate. Another method involves using a biomass material made of biomass olefins such as biomass ethylene and biomass propylene. １４ A crosslinking monomer containing C can be synthesized.

[0030] The preferred lower limit of the content of the crosslinkable monomer in the monomer composition is 0.1 wt%, and the preferred upper limit is 1.0 wt%. By setting the content of the crosslinkable monomer to 0.1 wt% or more, the effect as a crosslinking agent can be fully exerted, and by setting the content of the crosslinkable monomer to 1.0 wt% or less, the expansion ratio of the thermally expandable microcapsules can be improved. The more preferred lower limit of the content of the crosslinkable monomer is 0.15 wt%, and the more preferred upper limit is 0.9 wt%.

[0031] The monomer composition preferably contains a (meth)acrylic acid ester monomer. The (meth)acrylic acid ester monomer has one radically polymerizable double bond. The inclusion of the (meth)acrylic acid ester monomer improves the miscibility of the thermally expandable microcapsules with a matrix resin such as a thermoplastic resin, and the foamed molded article using the thermally expandable microcapsules has an excellent appearance.

[0032] The (meth)acrylic acid ester monomer may be a (meth)acrylic acid monoester monomer. Specific examples thereof include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate, and alicyclic, aromatic, and heterocyclic (meth)acrylic acid esters such as cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and isobornyl (meth)acrylate. The (meth)acrylic acid ester monomer preferably has a linear structure rather than a cyclic structure. Furthermore, the (meth)acrylic acid ester monomer is preferably a (meth)acrylic acid monoester. The (meth)acrylic acid ester monomer is most preferably a linear (meth)acrylic acid monoester.

[0033] The (meth)acrylic acid ester monomer is １４ It is preferable that the (meth)acrylic acid ester monomer contains C. １４ The method for obtaining the (meth)acrylic acid ester monomer containing C is not particularly limited. For example, it can be synthesized from commercially available biomass (meth)acrylate. Examples of the commercially available biomass (meth)acrylate include n-octyl (meth)acrylate, 2-octyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate, and tetrahydrofurfuryl (meth)acrylate. In addition, as another method, it can be synthesized using a biomass material consisting of a biomass olefin such as biomass ethylene or biomass propylene. １４ If cost is not a concern, any (meth)acrylic acid ester monomer containing C can be used. １４ Although it is possible to synthesize a (meth)acrylic acid ester monomer containing C, it is preferable to use biomass-derived methyl methacrylate because it is available at low cost.

[0034] The preferred lower limit of the content of the (meth)acrylic acid ester monomer in the monomer composition is 0.1 wt%, and the preferred upper limit is 30 wt%. By setting the content of the (meth)acrylic acid ester monomer to 0.1 wt% or more, the dispersibility of the composition using thermally expandable microcapsules can be improved, and by setting it to 30 wt% or less, the gas barrier properties of the cell walls can be improved, thereby improving thermal expansion. The more preferred lower limit of the content of the (meth)acrylic acid ester monomer is 1 wt%, even more preferred is 5 wt%, particularly preferred is 10 wt%, more preferably is 25 wt%, and even more preferably is 23 wt%.

[0035] The monomer composition preferably contains another monomer other than the nitrile monomer, the carboxyl group-containing monomer, the crosslinkable monomer, and the (meth)acrylic acid ester monomer. The other monomer is preferably at least one selected from vinylidene chloride, vinyl acetate, and a styrene-based monomer. The inclusion of the other monomer improves the miscibility of the thermally expandable microcapsules with a matrix resin such as a thermoplastic resin, and the foamed molded article using the thermally expandable microcapsules has an excellent appearance. Among these, vinylidene chloride is more preferred.

[0036] The preferred lower limit of the content of the other monomer in the monomer composition is 10 wt %, and the preferred upper limit is 25 wt %. By making the content of the other monomer 10 wt % or more, the dispersibility of the composition using the thermally expandable microcapsules can be improved, and by making it 25 wt % or less, the gas barrier properties of the cell wall can be improved, and the thermal expandability can be improved. The more preferred lower limit of the content of the other monomer is 15 wt %, and the more preferred upper limit is 22 wt %.

[0037] The monomer composition may contain a component other than the monomer. The component other than the monomer is preferably a resin component other than the monomer. Examples of the resin component include thermosetting resin, dextrin, gelatin, casein, shellac, gum arabic, cellulose, etc. Examples of the thermosetting resin include epoxy resin, phenol resin, urea resin, melamine resin, etc. Among them, epoxy resin is preferred from the viewpoint of improving heat resistance and durability. Note that thermosetting resins such as epoxy resin and cellulose are preferred. １４ It may also contain C.

[0038] The monomer composition preferably contains a metal-containing compound. By including the metal-containing compound, ionic crosslinking occurs between the carboxyl group of the carboxyl group-containing monomer, thereby increasing crosslinking efficiency and improving heat resistance. As a result, thermally expandable microcapsules can be produced that do not burst or shrink for extended periods of time at high temperatures. Furthermore, because the elastic modulus of the shell is not easily reduced even at high temperatures, the thermally expandable microcapsules do not burst or shrink even when subjected to molding processes that involve the application of strong shear forces, such as kneading, calendaring, extrusion, and injection molding. Furthermore, the ionic crosslinking, rather than covalent bonding, results in the particle shape of the thermally expandable microcapsules becoming closer to a perfect sphere, reducing distortion. This is thought to be due to the fact that crosslinking via ionic bonds has weaker bonding strength than covalent bonds, resulting in uniform shrinkage of the volume of the thermally expandable microcapsules during the conversion of the monomer to a polymer during polymerization.

[0039] Examples of the metal-containing compound include metal cation salts and metal-containing organic compounds. The metal cation of the metal cation salt is not particularly limited as long as it is a metal cation that reacts with the radically polymerizable unsaturated carboxylic acid monomer (II) to form ionic crosslinks, and examples include ions of Na, K, Li, Zn, Mg, Ca, Ba, Sr, Mn, Al, Ti, Ru, Fe, Ni, Cu, Cs, Sn, Cr, and Pb. Among these, ions of divalent to trivalent metal cations such as Ca, Zn, and Al are preferred, with Zn ions being particularly preferred. Examples of the metal cation salt include halides (chlorides, bromides, iodides), sulfates, and nitrates of the above-mentioned metal cations. These metal cation salts may be used alone or in combination of two or more.

[0040] In addition, when two or more of the above metal cation salts are used, the combination is not particularly limited, but it is preferable to use an alkali metal or alkaline earth metal ion in combination with a metal cation other than the alkali metal or alkaline earth metal. By having the alkali metal or alkaline earth metal ion, functional groups such as carboxyl groups are activated, and the reaction between the metal cation other than the alkali metal and the carboxyl group or the like can be promoted. Examples of the alkali metal or alkaline earth metal include Na, K, Li, Ca, Ba, Sr, etc., and among them, it is preferable to use Na, K, etc., which have strong basicity.

[0041] Examples of the metal-containing organic compound include alkyl metals, as well as metal chelate compounds, metal esters, metal acylates, metal alkoxides, etc. The metals in the metal-containing organic compounds can be the same as the metal cations described above.

[0042] The preferred lower limit of the content of the metal-containing compound is 0.1 wt % relative to the total amount of monomers, and the preferred upper limit is 10 wt %. By setting the content to 0.1 wt % or more, heat resistance can be improved, and by setting the content to 10 wt % or less, the expansion ratio can be improved. The more preferred lower limit is 0.5 wt % and the more preferred upper limit is 5 wt %.

[0043] The monomer composition contains a polymerization initiator to polymerize the monomer. Suitable examples of the polymerization initiator include dialkyl peroxides, diacyl peroxides, peroxyesters, peroxydicarbonates, and azo compounds. Suitable examples of the polymerization initiator include dialkyl peroxides, diacyl peroxides, peroxyesters, peroxydicarbonates, and azo compounds. Specific examples include dialkyl peroxides such as methyl ethyl peroxide, di-t-butyl peroxide, and dicumyl peroxide; and diacyl peroxides such as isobutyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, and 3,5,5-trimethylhexanoyl peroxide. Other examples include t-butyl peroxypivalate, t-hexyl peroxypivalate, t-butyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, 1-cyclohexyl-1-methylethyl peroxyneodecanoate, and 1,1,3,3-tetramethylbutyl peroxyneodecanoate. Other examples include peroxyesters such as cumyl peroxyneodecanoate and (α,α-bis-neodecanoylperoxy)diisopropylbenzene; bis(4-t-butylcyclohexyl)peroxydicarbonate, di-n-propyl-oxydicarbonate, and diisopropyl peroxydicarbonate. Further examples include peroxydicarbonates such as di(2-ethylethylperoxy)dicarbonate, dimethoxybutylperoxydicarbonate, and di(3-methyl-3-methoxybutylperoxy)dicarbonate. Additionally, examples include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and 1,1'-azobis(1-cyclohexanecarbonitrile).

[0044] The weight-average molecular weight of the polymer constituting the shell preferably has a lower limit of 100,000 and an upper limit of 2,000,000. When the weight-average molecular weight is 100,000 or more, a decrease in the strength of the shell can be suppressed, and when the weight-average molecular weight is 2,000,000 or less, an excessive increase in the strength of the shell can be suppressed, and a decrease in the expansion ratio can be suppressed.

[0045] The shell may further contain, as necessary, a stabilizer, an ultraviolet absorber, an antioxidant, an antistatic agent, a flame retardant, a silane coupling agent, a coloring agent, and the like.

[0046] The thermally expandable microcapsules of the present invention have a volatile expanding agent encapsulated in the shell as a core agent. The volatile expanding agent is a substance that becomes gaseous at a temperature below the softening point of the polymer that constitutes the shell, and is preferably a low-boiling organic solvent. Examples of the volatile expanding agent include low-molecular-weight hydrocarbons such as ethane, ethylene, propane, propene, n-butane, isobutane, butene, isobutene, n-pentane, isopentane, neopentane, n-hexane, heptane, petroleum ether, isooctane, octane, decane, isododecane, dodecane, and hexanedecane. Also, CCl ３ F, CCl ２ F ２ , CClF ３ , CClF ２ -CClF ２ and chlorofluorocarbons such as tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, trimethyl-n-propylsilane, and tetraalkylsilanes such as tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trimethyl-n-propylsilane. Among these, isobutane, n-butane, n-pentane, isopentane, n-hexane, isooctane, isododecane, and mixtures thereof are preferred. These volatile expanding agents may be used alone or in combination of two or more. Furthermore, as the volatile expanding agent, a thermally decomposable compound that is thermally decomposed into a gaseous form by heating may be used.

[0047] The volatile swelling agent is １４ It is preferable that C is contained. １４ The method for obtaining the volatile expanding agent containing C is not particularly limited, but １４ A method for making a volatile expanding agent containing C is preferred. １４Examples of methods for producing a volatile leavening agent containing C include a method of synthesizing the agent from bioalcohol obtained by fermenting sugar derived from plants; １４ Examples of methods include synthesis by reacting carbon monoxide containing C with hydrogen, a method of obtaining it by processing bio-crude oil, and a method of obtaining it from oils and fats extracted from microalgae. １４ As the volatile blowing agent containing C, a biomass hydrocarbon such as a commercially available biomass olefin (biomass ethylene) may be used, or a biomass saturated hydrocarbon synthesized by reducing a commercially available biomass olefin or the like may be used.

[0048] In the thermally expandable microcapsules of the present invention, among the above-mentioned volatile expanding agents, it is preferable to use low-boiling-point hydrocarbons having 5 or less carbon atoms. By using such hydrocarbons, it is possible to obtain thermally expandable microcapsules with a high expansion ratio and rapid expansion start. Furthermore, as the volatile expanding agent, a thermally decomposable compound that is thermally decomposed into a gaseous form when heated may be used.

[0049] The method for producing the thermally expandable microcapsules of the present invention is not particularly limited, but can be produced, for example, by carrying out the steps of preparing an aqueous medium, dispersing an oily mixture containing a monomer composition and a volatile expanding agent in the aqueous medium, and polymerizing the monomer.

[0050] When producing the thermally expandable microcapsules of the present invention, the first step is to prepare an aqueous medium. Specifically, for example, a polymerization reaction vessel is charged with water, a dispersion stabilizer containing silicon dioxide, and optionally a co-stabilizer to prepare an aqueous dispersion medium containing silicon dioxide. Furthermore, alkali metal nitrite, stannous chloride, stannic chloride, potassium dichromate, etc. may also be added as necessary.

[0051] Examples of the silicon dioxide-containing dispersion stabilizer include colloidal silica. As the colloidal silica, alkaline colloidal silica having a colloidal solution (aqueous dispersion) with a pH of more than 7 may be used, or acidic colloidal silica having a pH of less than 7 may be used. Of these, alkaline colloidal silica is more preferred. Furthermore, the colloidal silica preferably contains 10 to 50% by weight of silicon dioxide as a solid content and is monodispersed.

[0052] Examples of dispersion stabilizers other than silicon dioxide include calcium phosphate, magnesium hydroxide, aluminum hydroxide, ferric hydroxide, barium sulfate, calcium sulfate, sodium sulfate, calcium oxalate, calcium carbonate, barium carbonate, and magnesium carbonate.

[0053] The amount of the dispersion stabilizer containing silicon dioxide to be added is determined appropriately depending on the particle size of the thermally expandable microcapsules, but the preferred lower limit is 2.5 parts by weight and the preferred upper limit is 7 parts by weight relative to 100 parts by weight of the oily mixture (oil phase).The more preferred lower limit is 3 parts by weight and the even more preferred upper limit is 5 parts by weight.The amount of the oil phase refers to the total amount of the monomer and the volatile expanding agent.

[0054] Examples of the auxiliary stabilizer include a condensation product of diethanolamine and an aliphatic dicarboxylic acid, a condensation product of urea and formaldehyde, etc. Further examples include polyvinylpyrrolidone, polyethylene oxide, polyethyleneimine, tetramethylammonium hydroxide, gelatin, methylcellulose, polyvinyl alcohol, dioctyl sulfosuccinate, sorbitan ester, various emulsifiers, etc.

[0055] The combination of the dispersion stabilizer and the auxiliary stabilizer is not particularly limited, and examples thereof include a combination of colloidal silica and a condensation product, and a combination of colloidal silica and a water-soluble nitrogen-containing compound.Among these, a combination of colloidal silica and a condensation product is preferred.Furthermore, as the condensation product, a condensation product of diethanolamine and an aliphatic dicarboxylic acid is preferred, and a condensation product of diethanolamine and adipic acid or a condensation product of diethanolamine and itaconic acid is particularly preferred.

[0056] Examples of the water-soluble nitrogen-containing compound include polyvinylpyrrolidone, polyethyleneimine, polyoxyethylene alkylamine, polydialkylaminoalkyl(meth)acrylates such as polydimethylaminoethyl methacrylate and polydimethylaminoethyl acrylate, polydialkylaminoalkyl(meth)acrylamides such as polydimethylaminopropyl acrylamide and polydimethylaminopropyl methacrylamide, polyacrylamides, polycationic acrylamides, polyamine sulfones, and polyallylamines. Among these, polyvinylpyrrolidone is preferably used.

[0057] The amount of the above condensation product or water-soluble nitrogen-containing compound is determined appropriately depending on the particle size of the thermally expandable microcapsules, but the preferred lower limit is 0.05 parts by weight and the preferred upper limit is 0.2 parts by weight per 100 parts by weight of the oily mixture.

[0058] In addition to the dispersion stabilizer and co-stabilizer, inorganic salts such as sodium chloride and sodium sulfate may be added. By adding an inorganic salt, it is possible to obtain thermally expandable microcapsules with a more uniform particle shape. The amount of the inorganic salt added is usually preferably 0 to 100 parts by weight per 100 parts by weight of the monomer.

[0059] The aqueous dispersion medium containing the dispersion stabilizer is prepared by blending the dispersion stabilizer and / or co-stabilizer with deionized water, and the pH of the aqueous phase is determined appropriately depending on the type of dispersion stabilizer and / or co-stabilizer used. For example, when silicon dioxide is used as the dispersion stabilizer, polymerization is carried out in an acidic medium, and to make the aqueous medium acidic, an acid such as hydrochloric acid is added as necessary to adjust the pH of the system to 3 to 4. On the other hand, when magnesium hydroxide or calcium phosphate is used, polymerization is carried out in an alkaline medium.

[0060] Next, in the method for producing thermally expandable microcapsules, a step of dispersing an oily mixture containing a monomer composition and a volatile expanding agent in an aqueous medium is carried out. In this step, the monomer composition and the volatile expanding agent may be added separately to an aqueous dispersion medium to prepare an oily mixture in the aqueous dispersion medium, but typically the two are mixed together in advance to form an oily mixture, which is then added to the aqueous dispersion medium. In this case, the oily mixture and the aqueous dispersion medium may be prepared in separate containers, and the oily mixture may be dispersed in the aqueous dispersion medium by stirring and mixing in a separate container (primary dispersion), which may then be added to a polymerization reaction vessel. In addition, a polymerization initiator is used to polymerize the monomer. The polymerization initiator may be added to the oily mixture in advance, or may be added after stirring and mixing the aqueous dispersion medium and the oily mixture in the polymerization reaction vessel.

[0061] In the present invention, the monomers constituting the monomer composition are １４ By using a monomer containing C, the carbon 14 ( １４ C) abundance ratio ( １４ C / C) is 1.0 x 10 －１４ In addition to the above-mentioned monomers, a volatile expanding agent may be used to produce the thermally expandable microcapsules. １４ A volatile expanding agent containing C may also be used.

[0062] Examples of the step of dispersing the oily mixture containing the monomer composition and the volatile swelling agent in an aqueous medium include a method of stirring with a homomixer (for example, manufactured by Tokushu Kika Kogyo Co., Ltd.), a method of stirring with a stirring blade such as a retreating blade, a batch-type high-speed rotation high-shear disperser (for example, JP-A-7-96167), a continuous-type high-speed rotation high-shear disperser (for example, JP-A-2000-191817), etc. Further examples include a method of passing the mixture through an in-tube dispersing device such as a line mixer or a static in-tube mixer (static mixer).

[0063] The thermally expandable microcapsules of the present invention can be produced by subjecting the dispersion obtained through the above-mentioned steps to a step of polymerizing the monomer by heating, and a step of washing. The thermally expandable microcapsules produced by this method have a high maximum foaming temperature, excellent heat resistance, and do not burst or shrink even when molded at high temperatures.

[0064] The method for producing thermally expandable microcapsules of the present invention includes a washing step. Examples of the washing step include immersion washing, running water washing, and shower washing. Furthermore, washing methods that combine these with ultrasonic waves or vibration can also be applied. Furthermore, the washing step can be performed in combination with a dehydration step to improve production efficiency.

[0065] In the method for producing thermally expandable microcapsules of the present invention, a drying step is then carried out, which serves the purpose of volatilizing the liquid component and also adjusts the silicon dioxide content of the shell.

[0066] The drying step can be carried out using methods such as natural drying, hot air drying (fluidized bed drying), and vacuum drying. The drying temperature is preferably 30° C. or higher, more preferably 32° C. or higher, and even more preferably 35° C. or higher, and is preferably 70° C. or lower, more preferably 68° C. or lower, and even more preferably 65° C. or lower. The drying time (total drying time) in the drying step is preferably 12 hours or longer, more preferably 13 hours or longer, and even more preferably 14 hours or longer, and is preferably 20 hours or shorter, and more preferably 18 hours or shorter.

[0067] A hollow particle having a shell, wherein the carbon-14 ( １４ C) abundance ratio ( １４ C / C) is 4.0 x 10 －１４ The hollow particles described above are also one aspect of the present invention. The hollow particles can be produced, for example, by heating the thermally expandable microcapsules of the present invention to thermally expand them. The shell constituting the hollow particles of the present invention can be the same as that of the thermally expandable microcapsules of the present invention. In addition, in the hollow particles of the present invention, by adjusting the components of the monomers constituting the shell of the hollow particles, １４ It is possible to control the C / C ratio. １４ Using a monomer containing C, １４ It is preferable to use a monomer additive containing C. In addition, hollow particles produced by existing methods １４ Surface treatment using a material containing C, １４ By covering the hollow particles with a film containing a material containing C, １４ The C / C can be controlled.

[0068] A foam in which cells are dispersed in a resin, the cells of the foam being formed by thermal expansion of thermally expandable microcapsules each having a shell containing a polymer and a volatile liquid as a core agent, and the carbon content of the foam is 14 ( １４ C) abundance ratio ( １４ C / C) is 1.0 x 10 －１４ The foam described above also constitutes one aspect of the present invention. The thermally expandable microcapsules in the foam of the present invention can be the same as those in the thermally expandable microcapsules of the present invention. In addition, in the foam of the present invention, by adjusting the components of the monomer, volatile expanding agent, and resin that constitute the shell of the thermally expandable microcapsule, １４ It is possible to control the C / C ratio. １４ Using a monomer containing C, １４ Using an additive containing C, １４ Using a volatile swelling agent containing C; １４It is preferable to use a resin containing C. Examples of the resin include a bio-based elastomer (styrene-based [Septon (registered trademark)] manufactured by Kuraray Co., Ltd., bio content 80%), an olefin-based elastomer, etc. In addition, it is also possible to use a resin containing C in a thermally expandable microcapsule manufactured by an existing method. １４ Surface treatment using a material containing C; １４ Covering with a coating containing a material containing C, １４ Adding a material containing C (particles, etc.) also improves the foam's １４ The C / C can be controlled.

[0069] The foam of the present invention contains 14 carbon atoms ( １４ C) abundance ratio ( １４ C / C) is 1.0 x 10 －１４ That's all. １４ C / C is 1.0 x 10 －１４ By satisfying the above, it becomes possible to track the source of carbon dioxide while maintaining sufficient foaming performance. １４ The preferred lower limit of C / C is 2.0 × 10 －１４ , and a more preferable lower limit is 5.0 × 10 －１４ , and a more preferable lower limit is 1.0 × 10 －１３ , the preferred upper limit is 1.0 × 10 －１１ , and a more preferable upper limit is 7.0 × 10 －１２ , and a more preferable upper limit is 5.0 × 10 －１２ Note that total carbon is the sum of all carbon isotopes, １４ C / C is the ratio of carbon to total carbon １４ The abundance ratio of C.

[0070] In the foam of the present invention, the thermally expandable microcapsules may be the same as those of the thermally expandable microcapsules of the present invention. Furthermore, a thermoplastic resin is preferred as the resin. Specific examples of the thermoplastic resin include polyolefins such as low-density polyethylene (LDPE) and polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), vinyl chloride, polystyrene, thermoplastic elastomers, olefin-based thermoplastic elastomers (TPV), and ethylene-methyl methacrylate copolymer (EMMA). Among these, LDPE, EVA, EMMA, and the like are preferred due to their low melting points and ease of processing. These may be used alone or in combination of two or more.

[0071] Examples of methods for producing the foam of the present invention include a method of adding the thermally expandable microcapsules of the present invention to a resin and foam-molding the resulting mixture, a method of adding the hollow particles of the present invention to a resin and molding the resulting mixture, and a method of adding the thermally expandable microcapsules of the present invention to a resin or the like to prepare masterbatch pellets, and then adding a resin or the like to the masterbatch pellets and foam-molding the resulting mixture. In the foam-molding method, a foam can be produced by molding using a molding method such as injection molding, and then foaming the thermally expandable microcapsules by heating during molding.

[0072] The molding method for producing the foam of the present invention is not particularly limited, and examples thereof include kneading molding, calendar molding, extrusion molding, injection molding, etc. In the case of injection molding, the process is not particularly limited, and examples thereof include the short-short method in which a resin material is partially placed in a mold and foamed, and the core-back method in which the mold is fully filled with the resin material and then opened to the desired foaming point.

[0073] When preparing the masterbatch pellets, it is preferable that the masterbatch pellets contain 0.1 to 10 parts by weight of thermally expandable microcapsules per 100 parts by weight of resin.

[0074] The foamable resin composition may also contain a chemical foaming agent. The chemical foaming agent is not particularly limited as long as it is powdery at room temperature, and any conventionally commonly used chemical foaming agent can be used. Chemical foaming agents are classified into organic and inorganic foaming agents, each of which is further classified into thermal decomposition and reactive types. Commonly used organic thermal decomposition foaming agents include azodicarbonamide (ADCA), N,N'-dinitropentamethylenetetramine (DPT), and 4,4'-oxybisbenzenesulfonylhydrazide (OBSH). Examples of inorganic thermal decomposition foaming agents include bicarbonates, carbonates, and combinations of bicarbonates and organic acid salts. It is preferable to use a thermal decomposition chemical foaming agent. The performance of a thermal decomposition chemical foaming agent is determined by its decomposition temperature, gas generation rate, and particle size.

[0075] According to the present invention, it is possible to provide thermally expandable microcapsules, hollow particles, and foams that have sufficient foaming performance and are capable of tracing the source of carbon dioxide.

[0076] The following examples will further illustrate the present invention, but the present invention is not limited to these examples.

[0077] (Example 1) (Preparation of thermally expandable microcapsules) 130 parts by weight of colloidal silica with a solid content of 20% by weight, 6 parts by weight of polyvinylpyrrolidone, and 640 parts by weight of sodium chloride were added to 2,000 parts by weight of ion-exchanged water, mixed, and then adjusted to pH 3.5 to prepare an aqueous dispersion medium. １４ Acrylonitrile containing C, acrylonitrile [ １４ C-containing], 19.9 parts by weight of acrylonitrile synthesized from biomass propylene (manufactured by Asahi Kasei Corporation), 29.9 parts by weight of methacrylonitrile, 29.9 parts by weight of biomass-derived methacrylic acid ( １４ Methacrylic acid containing C, methacrylic acid [ １４ C-containing], 29.9 parts by weight of methacrylic acid synthesized from bioisobutanol (manufactured by Mitsubishi Chemical Corporation), 29.9 parts by weight of biomass-derived methyl methacrylate ( １４ Methyl methacrylate containing C, methyl methacrylate [ １４C-containing], 19.9 parts by weight of methyl methacrylate synthesized from bioisobutanol (manufactured by Mitsubishi Chemical Corporation), 0.4 parts by weight of trimethylolpropane trimethacrylate, and 0.25 parts by weight of zinc hydroxide were mixed to prepare a monomer composition in the form of a homogeneous solution. １４ Isopentane containing C, isopentane [ １４ 22 parts by weight of PEG-400 (containing PEG-400C, manufactured by Showa Cell Sekiyu Co., Ltd.) were added and mixed in an autoclave. The aqueous dispersion medium was then charged into the autoclave and stirred at 1,000 rpm for 10 minutes, followed by nitrogen substitution and a reaction at a reaction temperature of 60°C for 15 hours. The reaction pressure was 0.5 MPa and the stirring was at 200 rpm. 170 L of the resulting polymerized slurry was then fed to a compression dehydration device (manufactured by Ishigaki Co., Ltd., filter press) and dehydrated. 800 L of washing water was then fed to the dehydrator to perform a washing process, followed by drying to obtain thermally expandable microcapsules.

[0078] The above isopentane ( １４ C-containing isopentane) was synthesized by the following method. Hemicellulose in cellulosic biomass was hydrolyzed and saccharified to obtain xylose, which has 5 carbon atoms. The obtained xylose was hydrogenated to produce xylitol, a sugar alcohol with 5 carbon atoms. Pentane was obtained from the sugar alcohol with 5 carbon atoms, mainly consisting of xylitol, by hydrogenolysis. The obtained pentane was reacted in the presence of a catalyst to produce isopentane ( １４ C) was obtained.

[0079] (Examples 2 to 16, Comparative Examples 1 to 5) Acrylonitrile (Acrylonitrile [ １４ C-containing] or [ １４ C-free]), methacrylonitrile, methacrylic acid (methacrylic acid [ １４ C-containing] or [ １４ C-free]), methyl methacrylate (methyl methacrylate [ １４ C-containing] or [ １４C-free]), ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, zinc hydroxide, and colloidal silica were mixed in the compositions shown in Tables 1 and 2 to prepare monomer compositions, and then thermally expandable microcapsules were obtained in the same manner as in Example 1, except that the volatile expanding agents shown in Tables 1 and 2 were used. １４ C content] 22 parts by weight instead of isopentane [ １４ In Examples 3 to 9, 14 parts by weight of isopentane [ １４ In Example 13, 14 parts by weight of isopentane [C-free] and 10 parts by weight of isooctane were added. １４ C content] 22 parts by weight instead of isopentane [ １４ C content] 3 parts by weight, isopentane [ １４ In Comparative Example 4, 11 parts by weight of isopentane [ １４ In Comparative Example 2, 0.3 parts by weight of methylolpropane trimethacrylate and 20 parts by weight of isooctane were added. Furthermore, in Comparative Example 2, a metal chelate compound (titanium chelate compound, manufactured by Matsumoto Fine Chemical Co., Ltd.) was added in place of trimethylolpropane trimethacrylate.

[0080] Example 17 The thermally expandable microcapsules obtained in Example 8 were heated at 180° C. for 5 minutes (thermal expansion before molding) to obtain hollow particles.

[0081] Comparative Example 6 The thermally expandable microcapsules obtained in Comparative Example 3 were heated at 180° C. for 5 minutes (thermal expansion before molding) to obtain hollow particles.

[0082] (Evaluation Method) The performance of the obtained thermally expandable microcapsules and hollow particles was evaluated by the following methods. The results are shown in Tables 1 and 2.

[0083] (1) Evaluation of Thermally Expandable Microcapsules (1-1) Volume Average Particle Diameter The volume average particle diameter was measured using a particle size distribution diameter measuring instrument (LA-950, manufactured by HORIBA Co., Ltd.).

[0084] (1-2) Foaming Initiation Temperature, Maximum Foaming Temperature, and Maximum Displacement The foaming initiation temperature (Ts), maximum displacement (Dmax), and maximum foaming temperature (Tmax) were measured using a thermomechanical analyzer (TMA) (TMA2940, manufactured by TA Instruments). Specifically, 25 μg of a sample was placed in an aluminum container with a diameter of 7 mm and a depth of 1 mm, and heated from 80°C to 220°C at a heating rate of 5°C / min with a force of 0.1 N applied from above. The displacement in the vertical direction of the measuring probe was measured, and the temperature at which the displacement began to increase was defined as the foaming initiation temperature, the maximum value of the displacement as the maximum displacement, and the temperature at the maximum displacement as the maximum foaming temperature.

[0085] (1-3) Thermally expandable microcapsules, carbon 14 in the total carbon in hollow particles ( １４ C) abundance ratio ( １４ Measurement of C / C) The obtained thermally expandable microcapsules and hollow particles were subjected to CO2 measurement according to the pretreatment method (ASTM D6866 / Method B) specified by the American Society of Testing and Materials. ２ After that, they were converted to C (graphite) by complete reduction treatment using an iron catalyst. Then, the carbon isotope ratios ( １４ C / １２ C ratio, １３ C / １２ C ratio) and from the measurement results １２ C concentration, １３ C concentration and １４ The C concentration was calculated. １４ C concentration is the total carbon concentration ( １２ C concentration, １３ C concentration and １４ C concentration) in the thermally expandable microcapsules and hollow particles １４ The C / C was calculated. Here, graphite synthesized from an oxalic acid standard substance (HOxII) provided by the National Institute of Standards and Technology of the United States was used as the standard substance. １４ The detection limit of C / C is 1.0 x 10 －１４ In addition, the "shell" of the thermally expandable microcapsules１４ C / C" and "Core １４ C / C" was also measured, and "Shell １４ C / C" and "Core １４ C / C" [(in the core １４ C / C)-(shell １４ C / C)] and "Shell １４ C / C" versus "Core １４ C / C ratio [(in the core １４ C / C) / (shell １４ C / C)] was calculated.

[0086] (2) Evaluation of Foam (Preparation of Masterbatch Pellets) 68 parts by weight of low-density polyethylene (Petrothene 248, manufactured by Tosoh Corporation) as a base resin, 4 parts by weight of fatty acid ester as a lubricant, and 28 parts by weight of the thermally expandable microcapsules obtained in Example 8 and Comparative Example 3 were added and mixed, and the mixture was fed into a twin-screw extruder (TEM48SS, manufactured by Toshiba Machine Co., Ltd., same-direction type). Then, the cylinder temperatures in the regions near the raw material addition portion (C2 portion, C3 portion) were set to 98 ° C for C2 portion and 99 ° C for C3 portion, and kneading was performed. Note that the vent installed in the extruder was opened during extrusion. Next, the extruded strand was cooled by contacting it with water (submersion distance: 80 cm), and the strand was conveyed in the direction of the cutter. Then, it was cut using a strand cutter to pelletize, and masterbatch pellets were obtained.

[0087] (Production of Foam) 3 parts by weight of the obtained masterbatch pellets were mixed with 100 parts by weight of an olefin-based elastomer (TPO, manufactured by Mitsui Chemicals, Inc., Milastomer 7030BS), and the resulting mixed pellets were fed into the hopper of an extruder, melt-kneaded, and extrusion-molded to obtain a plate-shaped foam. The extrusion conditions were a mold temperature of 190°C. The foam using the thermally expandable microcapsules of Example 8 was designated Example 18, and the foam using the thermally expandable microcapsules of Comparative Example 3 was designated Comparative Example 7.

[0088] (2-1) Carbon 14 ( １４ C) abundance ratio ( １４Measurement of C / C) The obtained foam was subjected to CO2 measurement according to the pretreatment method (ASTM D6866 / Method B) specified by the American Society of Testing and Materials. ２ After that, it was converted to C (graphite) by complete reduction treatment using an iron catalyst. Then, the carbon isotope ratio ( １４ C / １２ C ratio, １３ C / １２ C ratio) and from the measurement results １２ C concentration, １３ C concentration and １４ The C concentration was calculated. １４ C concentration is the total carbon concentration ( １２ C concentration, １３ C concentration and １４ The total concentration of C in the foam is calculated by dividing the total concentration of C in the foam by the total concentration of C in the foam. １４ The C / C was calculated. Here, graphite synthesized from an oxalic acid standard substance (HOxII) provided by the National Institute of Standards and Technology of the United States was used as the standard substance. １４ The detection limit of C / C is 1.0 x 10 －１４ is less than.

[0089] (2-2) Carbon-14 ( １４ The obtained foam was subjected to CO2 detection by the pretreatment method (ASTM D6866 / Method B) specified by the American Society of Testing and Materials. ２ After that, it was converted to C (graphite) by complete reduction treatment using an iron catalyst. Then, the carbon isotope ratio ( １４ C / １２ C ratio, １３ C / １２ C ratio) and from the measurement results １４ The evaluation was carried out in the order of 3 g, 5 g, and 10 g of foam, and first １４The foam weight at which the C concentration was detected was evaluated according to the following criteria: 〇〇: Detected in foams of 3 g or more, 〇: Detected in foams of 5 g or more, △: Detected in foams of 10 g, ×: Not detectable in foams of 10 g or less.

[0090]

[0091]

[0092] According to the present invention, it is possible to provide thermally expandable microcapsules, hollow particles, and foams that have sufficient foaming performance and are capable of tracing the source of carbon dioxide.

Claims

1. A thermally expandable microcapsule in which a volatile expanding agent is encapsulated in a shell as a core agent, and the carbon content of the thermally expandable microcapsule is 14 ( １４ C) abundance ratio ( １４ C / C) is 4.0 x 10 －１４ That is all for the thermally expandable microcapsules.

2. The thermally expandable microcapsule according to claim 1, wherein the shell is made of a polymer of a monomer composition containing at least one monomer selected from the group consisting of nitrile-based monomers and monomers having a carboxyl group.

3. The shell is １４ Nitrile monomers containing C and １４ 2. The thermally expandable microcapsule according to claim 1, which comprises a polymer of a monomer composition containing at least one monomer selected from the group consisting of crosslinkable monomers containing C.

4. The thermally expandable microcapsules according to any one of claims 1 to 3, having a volume average particle size of 20 μm or more.

5. A thermally expandable microcapsule according to any one of claims 1 to 4, having a foaming initiation temperature (Ts) of 132°C or higher and 170°C or lower.

6. A thermally expandable microcapsule according to any one of claims 1 to 5, having a maximum foaming temperature (Tmax) of 170°C or higher and 220°C or lower.

7. The volatile swelling agent １４ The thermally expandable microcapsule according to any one of claims 1 to 6, comprising C.

8. A hollow particle having a shell, wherein the carbon-14 ( １４ C) abundance ratio ( １４ C / C) is 4.0 x 10 －１４ That's it, hollow particles.

9. A foam in which cells are dispersed in a resin, the cells of the foam being formed by the thermal expansion of thermally expandable microcapsules containing a volatile liquid as a core agent in a shell containing a polymer, and the carbon content of the foam is 14 ( １４ C) abundance ratio ( １４ C / C) is 1.0 x 10 －１４ That's it, foam.

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